Back to Basics: Thermal management for power supplies

One of the most important considerations in the design and selection of a power supply is its thermal management, says Arun Ananthampalayam of CUI. Here we examine the pathways for heat transfer and how power supply designs have evolved to enable effective heat dissipation and deliver greater performance.

Heat-dissipation efficiency has a direct impact on the performance of a power supply. Electronic circuits often perform more efficiently at lower temperatures and will in turn tend to dissipate less energy as wasted heat. The efficiency gains that can be obtained through effective cooling increase significantly as the power output of the overall system increases. Higher temperature operation can also have an effect on reliability. Systems that run cooler will have a lower probability of failing within a given time. These factors make it important to consider all possibilities when looking at the cooling options for power supply designs.

The first law of thermodynamics tells us how much heat needs to be dissipated from a given power-supply design. In brief:

Power In = Power Out.

Some of the energy that the supply takes in will be consumed by the internal electronics and converted into heat and this must be accounted for in the power equation. So:

Power In = Power Out + Power Dissipated as Heat.

The amount of power dissipated can be derived from the efficiency of the converter, which is calculated as the ratio of Power Out to Power In. The power dissipated as heat is therefore given by:

Thanks for the feedback. This is a new series so we were trying to judge the right level and wanted it to be accessible for all. Feedback is appreciated and we will keep this in mind for the next Back to Basics article. It's a quarterly series and the next one should appear in a few months time.

Basics, yes but I was hoping for something just a bit ahead of physics 101; how does the base board contact the heat sink; types of thermal compound vs insulating washers; variable speed fans; liquid cooling, etc. Maybe next article.